package com.yorick.common.util;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.tuple.Pair;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

@Slf4j
public class RSAUtils
{
    public static void main( String[] args ) throws Exception {
        //生成公钥和私钥
        Pair<String,String> key = getKeyPair();
        //加密字符串
        String password="token";
        System.out.println("随机生成的公钥为："+key.getLeft());
        System.out.println("随机生成的私钥为："+key.getRight());
        String passwordEn=encrypt(password,key.getLeft());
        System.out.println(password+"\t加密后的字符串为："+passwordEn);
        String passwordDe=decrypt(passwordEn,key.getRight());
        System.out.println("还原后的字符串为："+passwordDe);
    }
    /**
     * 随机生成密钥对
     * @throws NoSuchAlgorithmException
     */
    public static Pair<String,String> getKeyPair() throws Exception {
        //KeyPairGenerator类用于生成公钥和密钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        //初始化密钥对生成器，密钥大小为96-1024位
        keyPairGen.initialize(1024,new SecureRandom());
        //生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        PrivateKey privateKey = keyPair.getPrivate();//得到私钥
        PublicKey publicKey = keyPair.getPublic();//得到公钥
        //得到公钥字符串
        String publicKeyString=new String(Base64.encodeBase64(publicKey.getEncoded()));
        //得到私钥字符串
        String privateKeyString=new String(Base64.encodeBase64(privateKey.getEncoded()));
        //将公钥和私钥保存到Map
        Pair<String,String> response=Pair.of(publicKeyString,privateKeyString);
        return response;
    }
    /**
     * RSA公钥加密
     *
     * @param str
     *            加密字符串
     * @param publicKey
     *            公钥
     * @return 密文
     * @throws Exception
     *             加密过程中的异常信息
     */
    public static String encrypt(String str,String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey= (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RAS加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE,pubKey);
        String outStr=Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str
     *            加密字符串
     * @param privateKey
     *            私钥
     * @return 铭文
     * @throws Exception
     *             解密过程中的异常信息
     */
    public static String decrypt(String str,String privateKey){
       try{
           //Base64解码加密后的字符串
           byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
           //Base64编码的私钥
           byte[] decoded = Base64.decodeBase64(privateKey);
           PrivateKey priKey = KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
           //RSA解密
           Cipher cipher = Cipher.getInstance("RSA");
           cipher.init(Cipher.DECRYPT_MODE,priKey);
           String outStr=new String(cipher.doFinal(inputByte));
           return outStr;
       }catch (Exception e){
           log.error(e.getMessage());
       }
        return StringUtils.EMPTY;
    }
}